i'll try to explain again with some examples
ex1: are 1/4th notes they last for one beat of the metronome so to play this you should just play one note each note
ex2(starts at bar6 , oops): now this are 1/8th notes , every beat lasts for 1/4th note so now two 1/8th notes make up one 1/4th note, so in this example you would play two notes each beat.
ex3: now these are 1/16th notes , now we want 1/4th note each beat again so now 4 x 1/16th notes make 1/4th note again , so in this example you should play 4 notes each beat of the metronome
ex4: these are called three triplet 8th notes each one last 2/3 of a normal 8th note , so here there are trhee to make up 1/4th note, so here play 3 notes each beat, the last note is a dotted half note, so 1/2th note + 1/4th note so this last note lasts for 3 beats of the metronome .
well this works only if you're playing in 2/4,3/4,5/4 , etc..
well almost all songs are in one of these so no problem :)
for practicing scales i would advise to use 16th notes (4 a beat) and start slow...
hope you understand now?:p
otherwise i'll do another try:D